Like so many things in life, it all started with a girl. In fifth grade, the girl who sat next to Keith Hawkins every day in class would check out encyclopedias and look up subjects in astronomy, admiring pictures of swirling galaxies and colorful nebulae. Hawkins would join her, and the two of them would sit together and gaze at the heavens, one page at a time.

Earlier this month, Eris—the distant world first discovered by Caltech's Mike Brown and colleagues back in 2005, paving the way for the eventual demotion of Pluto from planet to dwarf planet—passed fortuitously in front of a faint star in the constellation Cetus. That passage, or occultation, allowed the first direct measurement of Eris's size.

As a kid, Assistant Professor of Astronomy John Johnson wasn't interested in astronomy—or even science for that matter. But now, as an assistant professor of astronomy, he's discovering entirely new worlds. In an interview, he talks about the search for planets and the rapidly evolving field of exoplanet astronomy.

Hundreds of extrasolar planets have been found, most solitary worlds orbiting their parent star in seeming isolation. Further observation has revealed that planets come in bunches. Most systems contain planets orbiting too far from one another to feel each other's gravity. In a handful of cases, planets have been found near enough to one another to interact gravitationally. Now, however, Caltech's John A. Johnson and his colleagues have found two systems with pairs of gas giant planets locked in an intimate orbital embrace.

Astronomers from Caltech and other institutions, using the highly sensitive 10-meter Keck I telescope atop Hawaii's Mauna Kea, have detected an extrasolar planet with a mass just four times that of Earth. The planet, which orbits its parent star HD156668 about once every four days, is the second-smallest world among the more than 400 exoplanets (planets located outside our solar system) that have been found to date.

An international team of astronomers has discovered the largest-radius and lowest-density exoplanet of all those whose mass and radius are known. It is a gas-giant planet about twice the size of Jupiter, and is likely to have a curved cometlike tail. It has been named TrES-4, to indicate that it is the fourth planet detected by the Trans-atlantic Exoplanet Survey (TrES) network of telescopes.

Astronomers using the Trans-atlantic Exoplanet Survey (TrES) network of small telescopes are announcing today their discovery of a planet twice the mass of Jupiter that passes in front of its star every 31 hours. The planet is in the constellation Hercules and has been named TrES-3 as the third planet found with the TrES network.

A team of astronomers led by Carl Grillmair of the California Institute of Technology has discovered some puzzling things about a Jupiter-sized planet that passes in front of a nearby star in the constellation Vulpecula.